1. Field of the Invention
This invention generally relates to a fabrication method of a memory element, and more particularly to a fabrication method of a non-volatile memory.
2. Description of Related Art
The non-volatile memory can save, read and erase data for multiple times, and the saved information can be retained even after power supply is off. With such advantages, the non-volatile memory has become a widely utilized element in personal computers and electronic devices.
A typical non-volatile memory element comprises a floating gate and a control gate thereon, made of doped polycrystalline silicon. Further, the floating gate and the control gate are isolated by an inter-gate dielectric layer, and the floating gate and the substrate are isolated by a tunneling layer. Besides, a source region and drain region are further disposed in the substrate at two sides of the control gate.
When writing data in a memory, a bias voltage is applied to the control gate, the source region and the drain region, for injecting electrons into the floating gate. When reading the data from the memory, an operational voltage is applied to the control gate. Meanwhile the charged electrons representing the state of the floating gate can affect the switch-on and the switch-off of the channel under the floating gate, which is utilized as a reference to determine the information value as “0” or “1”. When erasing the information at the memory, the relative electric potentials of the substrate, the source region, the drain region or the control gate are increased, such that the electrons, in a tunneling effect, could go from the floating gate to the tunneling layer and exit to the substrate (a substrate erase process), or pass through the inter gate dielectric layer and exit to the control gate.